Oral care products such as toothpastes and mouthwashes are routinely used by consumers as part of their oral care hygiene regimens. Oral care products are formulated to provide both therapeutic and cosmetic hygiene benefits. Therapeutic benefits include caries prevention which is typically delivered through the use of various fluoride salts; gingivitis prevention by the use of antimicrobial agents such as triclosan, cetylpyridinium chloride, stannous fluoride, zinc citrate or essential oils; and hypersensitivity control through the use of ingredients such as strontium chloride, stannous fluoride or potassium nitrate. Cosmetic benefits include control of plaque and calculus formation, removal and prevention of tooth stain, tooth whitening, breath freshening, and overall improvements in mouth feel impression which can be broadly characterized as mouth feel aesthetics. For example, agents such as pyrophosphate salts have been used as antitartar agents and polymeric agents such as condensed phosphorylated polymers, polyphosphonates, and carboxylated polymers have been used in oral care compositions to provide benefits including tooth surface conditioning and control of tartar, staining and astringency. To illustrate further, commonly assigned U.S. Pat. No. 6,555,094 to Glandorf, et al. discloses oral care compositions comprising a stannous ion source, a fluoride ion source, and a polymeric mineral surface active agent that binds stannous, wherein the compositions provide effective antimicrobial activity for reducing plaque and gingivitis with minimal side effects of tooth staining and astringency. The compositions simultaneously provide reduction and control of supragingival calculus. Additional disclosures related to the use of polyphosphate as mineral surface active agent in oral care compositions include commonly assigned U.S. Pat. No. 5,939,052; U.S. Pat. No. 6,187,295; U.S. Pat. No. 6,350,436; and U.S. Pat. No. 6,190,644.
Another benefit that is increasingly important for complete oral health is providing protection and resistance of teeth against erosion and wear, which is a permanent loss of tooth substance from the surface due to the action of chemicals, such as harsh abrasives and acids. Dental erosion may be caused by extrinsic or intrinsic factors. Extrinsic erosion is the result of oral consumption of dietary acids such as acidic beverages or fruit juices and environmental factors such as exposure to airborne contamination or acidic water in swimming pools. Intrinsic erosion is caused for example by endogenous acids produced in the stomach and which contact the teeth during the processes of vomiting, regurgitation or reflux. The main cause of regurgitation and induced vomiting are eating disorder conditions such as nervous vomiting, anorexia or bulimia (Moss, 1998, Int. Den. J., 48, 529).
The incidence and severity of dental erosion is on the rise with the increase in the consumption of acidic beverages and juices. The pH and titratable acidity of acidic beverages have been identified as the main causative agents in the initiation and progression of dental erosion (Lussi, 1995, Caries Res. 29, 349). Thus methods have been disclosed to modify acidic food and beverage products in order to prevent their erosive effect on teeth. See for example, U.S. Pat. No. 5,108,761 and WO 01/52796 both assigned to The Procter & Gamble Company; U.S. Pat. No. 6,383,473; U.S. Pat. No. 6,319,490; WO 01/72144; and WO 00/13531 all assigned to SmithKline Beecham; CA 1018393 assigned to General Foods Corporation; U.S. Pat. No. 3,471,613 and BE 638645, both assigned to Colonial Sugar Refining Co; and U.S. Pat. No. 4,853,237 assigned to Sinebrychoff Oy. In addition there have been disclosures of oral care compositions comprising agents indicated to provide teeth with antierosion or acid resistance benefits. See for example, JP 2001/158725; U.S. Pat. No. 4,363,794 and U.S. Pat. No. 4,335,102 all assigned to Lion Corporation; U.S. Pat. No. 5,130,123 assigned to The University of Melbourne; WO 99/08550 and WO 97/30601 both assigned to SmithKline Beecham; U.S. Pat. No. 3,914,404, assigned to Dow Chemical Co.; and U.S. Pat. No. 3,105,798, assigned to The Procter & Gamble Co.
One mechanism to provide erosion protection and maintain tooth integrity is described in U.S. Pat. No. 6,685,920 by use of oral compositions comprising certain chemical agents that have affinity for the tooth surface. These agents either bind to the tooth surface or form insoluble compounds or complexes on the tooth surface, thereby forming a protective film or coating. Examples of useful agents are polymeric mineral surface active agents such as phosphorylated polymers, in particular polyphosphates that bind to teeth, or metal ions such as stannous, zinc or copper that form insoluble compounds that deposit onto teeth, and combinations thereof. The polymeric coating or insoluble precipitate deposited onto teeth act as a protective layer that prevents erosive chemicals from contacting the tooth surface and etching away tooth hard tissue.
Caries is another condition that is detrimental to tooth health and structural integrity. The tooth caries process results in calcium phosphate mineral loss from tooth substrate induced by localized plaque microbiological acid production from fermentable dietary substrates. If left uninhibited, the caries process results in sufficient mineral loss from teeth, which manifests as a loss of structural integrity and the formation of a cavity. (G. H. Nancollas, “Kinetics of de- and remineralization,” pp 113-128; A. Thylstrup, J. D. B. Featherstone and L. Fredebo, “Surface morphology and dynamics of early enamel caries development,” pp 165-184 in: Demineralisation and Remineralisation of the Teeth, IRL Press Ltd., (1983). S. A. Leach and W. M. Edgar, editors). The caries process is not continuous but is described by cyclic periods of mineral loss from teeth, particularly following ingestion of fermentable carbohydrates, followed by periods of no mineral loss or even mineral repair of damaged local regions. Remineralization refers to the process of repair of acid damaged tooth structure—by the recrystallization of mineral salts on the tooth architecture. Remineralization processes are a natural protective feature of saliva against the formation of tooth cavities, as saliva is supersaturated with respect to calcium phosphate tooth mineral salts. Remineralization is accelerated by fluoride ions in solution which increase local supersaturation with respect to fluoridated calcium phosphate deposition. Fluoride uptake or fluoridation refers to the acquisition of fluoride into tooth substrates resulting from topical treatments with fluoride agents. Often, but not always, remineralized teeth from treatments exhibit increases in fluoride uptake and retention. Demineralization is the process of mineral loss from teeth caused by plaque acids or dietary acids. Demineralization can occur on tooth surfaces or below tooth surfaces depending upon the composition of the acids, concentration and pH. Moreover the teeth with increased remineralization and fluoride uptake and retention also exhibit superior resistance to acid demineralization. The processes of fluoride incorporation into teeth, remineralization and resistance to demineralization represent primary mechanisms toward the reduction of tooth decay or other acid insults.
In addition to fluoride agents, it is also advantageous to incorporate antimicrobial agents in oral care compositions in order to control plaque bacteria and prevent plaque formation and acid production, which is a pre-requisite step of the caries process.
Thus daily oral care at home requires products with multiple ingredients working by different mechanisms to provide the complete range of therapeutic and aesthetic benefits, including anticaries, antimicrobial, antigingivitis, antiplaque, antisensitivity, anticalculus and anti-erosion, as well as antiodor, mouth refreshment and moisturization, stain removal, stain control and tooth whitening. Formulating oral care products that contain different ingredients to provide the required range of benefits therefore presents a challenge in that these ingredients need to act in concert and not interfere with each other's activity. The present invention is thus directed to oral care compositions comprising selected organophosphate compounds that provide protection against tooth erosion and tooth wear in combination with one or more oral care actives including fluoride agents, antiplaque/antimicrobial agents and anticalculus agents.